Usually a digital camera uses a single-plate type of CCD or CMOS sensor, which is an arrangement of lots of picture-taking elements or photodiodes. These picture-taking elements lack the color discriminating capability, and therefore, the sensor is used along with a color filter. There are two different color filters; one is of the type of using three primary colors (red, green and blue) and the other is of the type of using the complementary colors C, M and Y (abbreviated for cyan, magenta and yellow). The former is called “Primary Color Filter”, and the latter is called “Complementary Color Filter”. The typical primary color filter is a lattice arrangement of green elements with red and blue elements sandwiched therebetween to be in conformity with the Bayer primary color system. On the other hand the typical complementary color filter consists of an arrangement of cyan, magenta and yellow components, and additional green component, which human eyes are sensitive to. In taking color pictures with a digital camera a mosaic color filter is laid on its sensor, allowing each sensor element to detect a beam of light passing through the overlying color filter element, thus performing a required detection in respect of colors. Specifically each sensor element collects only one piece of primary color information, and the undetectable part of the color picture is interpolated, so that a final image may be provided.
FIG. 6 shows the sequential image-processing steps, illustrating how the color image data from a digital camera, which is equipped with a CCD sensor and an associated color filter of the Bayer primary color system, is processed to obtain a final image.
The incident light is thrown onto the picture-taking section 12 via the lens 11. The light is converted into electric signal in the picture-taking section 12, and then is subjected to A/D conversion so that the digital data of the color image appears at the output terminals of the picture-taking section 12. Such digital data of color image is diagrammatically shown as a piece of color image data 101. As seen from the color pattern 101, the data structure comprises lots of red, blue and green constitutional components R, B and G recurrently arranged exactly in the same pattern as the primary Bayer system. In the original picture treating section this color image data 101 is subjected to the lens tone correction, white balance and any other treatments which are required for retouching the original picture. Then, in the data dividing section 14 the so treated image data is separated into three sub-pieces of color image data, each representing constitutional image pieces in respect of the three primary colors R, G and B. These sub-pieces of color image data are diagrammatically shown at 102. As seen from the color patterns 102 the red-representative image data is a representation of red elements distributed in the original picture 101, the sum of “R”-distribution squares being equal to one fourth or quarter (¼) of the whole sensor plane; the blue-representative image data is a representation of blue elements distributed in the original picture 110, the sum of “B”-distribution squares being equal to one fourth or quarter (¼) of the whole sensor plane; and the green-representative image data is a representation of green elements distributed in the original picture 110, the sum of “G”-distribution squares being equal to one half (½) of the whole sensor plane. Every data-absent or blank square is interpolated in the interpolating section 15. These sub-pieces of color image data provided at this step are diagrammatically shown at 103. It should be noted that the data points of each piece of mono-color image data 103 are equal to those of the picture-taking elements of the camera's sensor in number. These mono-color image data are subjected to YUV conversion in the YUV converting section 16, and then, to the secondary treatment such as contour highlight and gamma correction. The so treated data are outputted from the output section 18, and then subjected to the most-adaptability treatment in the “turning-to-being-most-adaptive-to-display” section 19. Finally the image data is displayed on the display unit 20 or stored in the storage medium 21.
Personal computers, cellular phones, PDAs (portable information terminals for individuals) and other information technology units have been developing these days, and some of those devices have cameras built therein. Under the circumstances it is required that the image data from the output unit 18 is not only stored or displayed but also sent via telephones, Bluetooth or any other wireless communication means to different receiving ends. For example, such output data of picture is attached to an e-mail.
As described above, the conventional image processing method causes the output data to increase three times as large as the original picture in quantities. As is well known, the cellular phone, PDA or any other portable information unit which is going to be redesigned to have a digital camera built in, is required to perform a variety of operations such as execution of some applications and communications, and accordingly it is necessary that the quantities of the data allotted for individual operation be reduced to minimum possible. Disadvantageously the conventional data processing method makes the output data amount increase three times as large as the data amount which is determined from the sensor's definition. In order to permit such a portable information device to accommodate the output data, therefore, it is unavoidable to lower the sensor's definition at the sending end. As for a signal bus between the portable information device and the digital camera it is necessary that its band width be expanded wide enough to accommodate the large quantities of output data. Such broad-band bus cannot be practically used because of the cost and space available in the device. As a matter of fact these make it difficult to build a digital camera in the portable information device.
Another problem is that: as long as the portable information device uses the conventional image processing method in handling the image data from the digital camera the image data cannot be processed at an increased efficiency. Generally speaking, the displays of portable information devices are small in size, and some of such displays can show only monochrome images. On the other hand the camera is much higher in definition than the display of the information device, and accordingly the information device wastes or discards some of the lot of image data in transforming into and showing images on the display of the information device. Incorporation of images into e-mails requires no images of high-definition. Therefore, it is demanded that the image data be so controlled in quantities that a relatively small amount of image data be used in the portable information device and that a relatively large amount of image data be used to provide high-definition images, for example for high-definition printing.
In view of the defects of the prior art as described above one object of the present invention is to provide an image processing apparatus or method capable of reducing a relatively large amount of output image data from a high-definition camera to a relatively small amount of output data as required.
In view of the defects of the prior art as described above another object of the present invention is to provide an image output unit capable of reducing a large amount of output image data in a high-definition camera to as small amount of output data as would be required by a portable information device.
In view of the defects of the prior art as described above still another object of the present invention is to provide a digital camera or portable information terminal device equipped with an image processing unit which is capable of curtailing the image data from the high-definition camera.
In view of the defects of the prior art as described above yet another object of the present invention is to provide a digital camera or portable information terminal device equipped with an image output unit which is capable of controlling the image data from the high-definition camera in quantities and providing the output image data of controlled amount to meet the need of the portable information device.